Means for producing gyratory motion



May 14; 1940. s. D. ROBINS MEANS FOR PRODUCING GYRATORY MOTION FiledJan. 18, 1937 3 Sheets-Sheet 1 INVENTOR SAMUEL 0. ROB/N5 y 1940- s. D.ROBINS 2.200.724

MEANS FOR PRODUCING GYRATORY MOTION Filed Jan. 18, 1937 SShetS-Sheet 2FIG. 4.

INVENTO BY :2 a

ATTORNEY R l SAMUEL 0. ROB/NS y 1940- I s. D. ROBINS 2.200.724

MEANS FOR PRQDUCING GYRATORY MOTION Filed Jan. 18, 1937 3 Sheets-Sheet 3,INVENTOR SAMUEL 0. ROB/N8 Y'ATTORNEY Patented May 1 9 UNITED STATESPATENT OFFICE MEANS FOR PRODUCING GYBATOBY MOTION This invention relatesto an improved means of imparting a gyratory movement to a freelysuspended body or a body otherwise supported for movement in a gyratorypath. A particular application ofthe invention is the production, by theimproved means, of a gyratory motion in a screen used for screeningcoal, stone and the like.

An important feature of the invention is the 10 production of a gyratorymotion through a noncircular orbit. This is especially useful inconnection with screens.

Heretofore screens have ordinarily been given .either a so-calledstraight line, reciprocatory motion or a circular, gyratory motion. Eachof these has certain advantages over the other. A 'reciprocatory screenhas the advantage of more rapidly advancing the material along itssurface. However, in doing this there is the danger that material of asize that should pass through the openings of the screen will not do sobecause it is not presented to any of the openings in quite 'the rightway. A gyratory screen having a circular motion has the advantage ofcausing the lumps of material, particularly the larger ones, to turn orroll over as they progress and thus they are presented in a variety ofdifferent positions to the successive openings. This effects a very goodseparation of themateri'al into the'desired classifications. However, agyratory screen of this type willadvance the material only very slowlyunless it is disposed at a fairly steep angle to the horizontal. notalways available to bring about a'desired feeding action.

By imparting a non-circular, substantially elliptical, gyratory motionto a screen the combined advantages of a reciprocatory and circular.motion are obtained. A very rapid feeding action is obtained with thescreen surface arranged horizontally and at the same time the gyratorymotion tends to turn or rotate the lumps so that a very good separationbetween the different sizes iseffected. For uniform and mostsatisfactory results the motion of the entire screen should be uniform,i. .e., all portions of the screen should describe the same path. Aspecial object of the invention has been to provide particularly simplebut effective means for producing a smooth, uniform, non-circular orelliptical, gyratory motion of a screen or other body. This, Iaccomplish by freely supporting the screen for movement in alldirections and imparting to it the effect of aresultant force which isconstantly changing in direction and Suflicient head room is magnitudeapplied at its center of gravity. If the resultant force applied at thecenter of gravity of the screen were indicated as vectors radiating froma point, representing the-center of gravity, a line connecting the endsof the 5 vectors would indicate the path or orbit traced by every pointon the screen, and this, according to the present invention, would besubstantially in the form of an ellipse. Such a resultant of constantlychanging direction and magnitude w may conveniently be produced byimparting to the screen a rotating force of constant magnitude and atthe same time imparting to the screen another force designed to workagainst and partially counteract or modify the rotating force as m thelatter passes through its cycle. This may be accomplished in avariety ofdifferent waysI .The constant rotating force may most easily be createdby the rotation of .a mass about a point removed from its center, themass being carried 2% in a suitable way by the body to be gyrated. Themodifying force may be created in a simple way, by a non-rotatinginertia mass arranged to increase the inertia of the body or itsresistance to movement to a greater extent in certain 26 directions thanin others. Or the modifying force may be imparted byianother rotatingmassof appropriate magnitude and in suitable relation to the firstrotating mass to-provide the desired resultant effect at the center ofgravity 30 of the body. In the preferred arrangement the desiredgyratory motion is brought about through the rotation, in oppositedirections, of masses of different magnitude or otherwise capable ofestablishing centrifugal forces of different magnitude. The masses maybe arranged to apply their centrifugal forces to the screen or otherbody directly at the center of gravity of the latter or at pointsremoved from such center but so se- 40 lected that no moments will beset up about said center. The two masses should be rotated at the samespeed to insure a desired synchronous relation between them and theirrelation should be such that their centrifugal forces at certain in- 45stants are created along the same or parallel lines so as to be directlycombined in their effects at a chosen angle to the horizontal. Forexampic, I have found that a very desirable screening ,action isproduced by a substantially elliptical so motion, the major axis ofwhich is disposed at an angle of about 40 to the horizontal. This may beaccomplished by a pair of counterrotating forces if the forces arecoincident or parallel and combined along the desired 40 line 66 and arecoincident or parallel and opposed along -the forces, their sumsdetermining the major axis and their differences the minor axis of theelliptical path or orbit. However, it is not generally convenient toapply the centrifugal forces to a screen directly at the center ofgravity or directly in line with such center at opposite sides of thescreen. This is for the reason that a shaft extending through the screenat this point will ordinarily fall in or near the path of travel of the-material to be screened; Accordingly, a special feature of theinvention is the provision of an arrangement by which rotating forces ofunequal magnitude may be applied to the screen, or other body, at pointsremoved from its center of gravity and in such a way that a uniformmotion will be imparted to all parts of the screen. This I preferablyaccomplish by establishing certain definite relationships between a pairof revolving masses and the center of .gravity of the body to begyrated. The masses are mounted on the body and impart their centrifugalforces to the body at their centers of rotation, these being spacedfromthe center of gravity of the body at distances inversely proportional tothe magnitude of the centrifugal forces. The unequal centrifugal forcescreated by the revolving masses are at times directly .combined and atother times directly opposed while between these two conditions theyhave components that combine and components that oppose each other,

and the net effect is the resultant of the'two moments are created aboutthis center.

. away to show in Other objects, features and advantages of theinvention will appear from the detailed description of an illustrativeform of the same, as applied to a screen structure, which will now begiven' in conjunction with the accompanying drawings, in which:

Figure 1 is a side elevation of a screen embodying the invention, aportion being broken section certain of the operating devices.

Figure 2 is a front elevation of the screen with a portion broken awayto disclose the operating devices.

Figure 3 is a diagram illustrating the relationship between certainforces created by the operating devices at one instant in the operationof the screen. I

Figure 4 is a diagram resolving the forces of Figure 3 and showing theresultant thereof.

Figure5 is a view similar 'to Figure 3, showing the forces existing at adifferent instant in the operation of the screen.

Figure 6 is a similar force diagram indicating the relationship of the.forces after they have passed through 90 from the position indicated inFigure-5.

Figuresf to 11, inclusive; are schematic views indicating a variety ofdifferent. arrangements -applying counter-rotating forces to a freely,

views showing mcansfor. imparting an elliptic motion to a screen throughthe usof one or more inertia masses, and

Figure 16 is a diagram illustrating the orbital path of ,each and .everypoint on a screen operated. in accordance with Figures 7 to' 15,inclusive.

Referring now to the drawings, and more particularly Figs. 1 and 2,there is shown a screen structure including a frame I0 adapted toreceive a gyratory motion of the improved type.

This frame maybe of any suitable construction,

and, by, way of example, may be provided with a pair of screeningsurfaces H and I2 extending horizontally across the same throughout thelength of the frame. The screen elements If and 12 may be of anysuitable construction and may be secured to the frame in any convenientmanner.

Adjacent each of the four corners of the frame there is provided asupporting spring l3 which at its upper end is engaged by a bracket l4bolted or otherwise secured to the side of the frame. At its lower endeach spring engages the top of a suitable support I 5 secured to anappropriate foundation, the members l5 and the foundation constituting amain supporting .frame. The springs l3 are preferably quite soft andreadily compressible so that the natural period of vibration of thesprings and supported mass will be low. This will preventany danger ofundue ina good insulation against the transmission of vibrations fromthe live frame to thesupporting structure. As indicated, each spring, ifdesired, may be ,formed in two sectionshaving a thin plate insertedbetween their abutting ends.

The devices for impartinga gyratory movement to the screen framearecarried by a housing l6 which extends across the top of the frame andis supported by the latter. It may be secured to the frame in anysuitable way, as by means of brackets ll extending I inwardly from the.slde walls of the frame and plates I8 extending upwardly from the outerfaces of these walls. Housings l9 and 20, at the opposite ends of thehousing l6, provide bearings I90 and 200 for a pair of shafts 2| and 22,which extend across the top of the frame If] within the housing l6.These housings l9 and 20, which are firmly secured to the frame l0,furthermore, enclose inter-meshing gears 23 and 24 secured to. theopposite ends of the shafts 2f and-22. A pulley 25 secured to anextension of the shaft 22 is connected by a belt 26 with apulley 21carried by the shaft of a motor 28, or is otherwise connected with asuitable source of power.

A bar 29 of appropriately chosen mass extends full distance between theshaft bearings. This bar may be secured to the shaft in any suitableway, as by means of bolts 30. Similarly, a bar 3|extending'longitudinally of the shaft 22jmay be secured thereto by meansof bolts 32. As best indicated in Figure 1, the bars 29 and 3| are ofdifferent sizes in cross-section, 'so as to provide longitudinally ofthe shaft 2| substantially the masses of different magnitude-adapted tobe revolved, respectively, about -the axes of the'shaf'ts 2| and 22. Thegearing 23, '24 is such that the two shafts-will rotate at the sameangular speed but in opposite directions. they'are rotated, I

axis of rotation., Thus, if Bdesignates the centrifugal forces will bedevelopedwhich for of the shaft 22 and E designates the center of themass 3|, the centrifugal force will always be radially outward along theline BE, the direction of which is, of course, constantly changing.Similarly, if C designates the axis of the shaft 2| and G designates thecenter of the mass 29, an outward, radial force will be created alongthe line CG in the course of rotating the shaft 2|. For reasons to bepresently explained, .a definite, angular relationship should existbetween the lines BE and CG. Assuming that the center of gravity of theframe l together with'the superposed operating mechanism, all of whichconstitutes what may be designated thedive frame, is

located at the point designated A in Fig. 1, the

masses 29 and 3! should be so located that when a straight line may bedrawn through the points A, B and E, a straight line may similarly bedrawn through the points A, C and G. This 9 means that when thecentrifugal force created by one of the. masses passes directly throughthe center of gravity, the centrifugal force created by the other masswill do likewise. Another relationship which should exist between theparts is 5 that the distance from A to B should be to the distance fromA to C as the centrifugal force produced by the bar 29 is to thecentrifugal force produced by the bar 3|. In other Words, thesecentrifugal forces should be inversely proportional (I to the distancesof the centers of rotation of the massesproducing them from the centerof gravity of the frame structure. In the construction illustrated, thecenters of the two masses are equally distant from their axes ofrotation, i. e., the distances BE and CG are the same. Accordingly, themasses themselves are inversely proportional to the distances of theiraxes of rotation from the center of gravityof the frame. In lieu ofselecting masses of different magnitude, the

0 distance from B to E might be made greater than the distance from C toG so that the centrifugal forces created by masses of equal magnitudeand rotated at the same speed would be inversely proportional to thedistances from the points of aps plication of these forces to the centerof gravityof the frame.

. As a specific example of a construction which I have found to be quitesatisfactory, the masses 29 and 3| may be in the ratio of 3 to 4 and thean distances AB and AC should then also be in the ratio of 3 to 4.Assuming now that the masses are being rotated in opposite directions atan appropriate speed, say 1100 R. P. M., the forces existing at aninstant when the points A, B and 55 E are aligned are illustrated inFigure 3. Here the force created by the mass 3! is indicated by arrow Fbwhile the force created by the mass 29 is indicated by the arrow Fc.Since these forces pass directly through the center of gravity of m theframe, it will be apparent that no turning moment will be applied to theframe and the effect will be merely to impart a translational movementto the entire frame. This movement will be in proportion to theresultant of the two 15 forces. Referring to Figure 4. wherein theforces are indicated on a larger scale, the resultant is designated bythe arrow Fr. Its magnitude is nearly but not quite the maximum that isapplied to the screen. I Fig e 5 indicates diagrammatically thedirection a magnitude of the forces when their resultant is greatest.This is whenthe two forces are acting in the same direction alongparallel lines. Considering the typical construction mentloned above, inwhich the two forces Fit and Fe arms of the forces Fb and Fe withrespect to the center of gravity A are in the ratio of three to fourand, therefore, the product ofone force 'times its moment arm will bethe same as the product of the, other force times its moment arm, andthere will be no turning moment created about the center of gravity ofthe body. The resultant force tending to impart bodily movement to thescreen will be at its maximum, 1. e., the

, sum of the two forces or seven units. In arriving at the positionsindicated by Fig. 5 the centers E and G of the masses 3| and 29 willhave turned from the positions indicated in Figs. 1 and 3 through halfof the angle BAC. Accordingly, this maximum force created under theconditions indicated in Fig. 5'will be in a direction parallel with theline AD (Figs. 1 and 3) which bisects the angle BAC. Very good screeningresults will be obtained if this line is disposed at an angle of about40 to the horizontal, although this may be varied considerably'to suitparticular requirements.

The relation of the forces after a rotation of' the masses 29 and 3|through an angle of 90 from the position indicated in Fig. 5 is showndiagrammatically in Fig. 6. Inasmuch as the masses are rotating at thesame angular velocity, the magnitude of the forces will remain the same,i. e., force-Fb will continually remain at four units and the force Fc.will remain at three units, Moreover, the moment arm of the two forceswill remain in the same relation and the forces will tend to createturning moments of I equal magnitude in opposite directions about thecenter of gravity of the .frame. Accordingly,

,there will be no tendency for the frame to rotate i have a magnitudeequal to the difference between the two. forces. In the typical exampleillustrated, this resultant will be one unit.

Any number of force diagrams may be drawn to indicate therelationbetween the two rotating forces at points intermediate thoseindicated in Figs. 3, 5 and 6. It will be found in all cases that theturning moments about the center of gravity of the body are balanced andif the resultants of the two ,forces with respect to this center areplotted and a line is drawn through the ends of the arrows, it will befound that a substantially elliptical configuration will be produced,the major axis of the ellipse being seven, units in length and the minoraxis being one unit. Since the screen frame 10 is supported forrelatively free movement in all directions. it will be apparent that theconstantly changing resultant, changing not only in direction but inmagnitude, will impart a corresponding change in the move ment of theframe- After the frame has been set into motion at the desired speed, itwill be found to follow through a smooth, substantially elliptical,gyratory path, Whose major axis is in the direction AD. As previouslystated, the motion so produced has been found ideally suited for thescreening of coal. stone and the like. It'will 1 and 2', are alsomaintained. 'll

Accordingly, movement of the screen along this major axi will havelittle or no effect upon the tension of the belt. At the same time themovement of the screen along the minor axis is so small that it isreadily permitted by the belt and I does not appreciably interfere withthe drive of the belt.

' A more uniform action of the screen is insured if the upper ends ofthe springs l3, i, e., the points at which they support the screenframe, are in a plane passing substantially through the center ofgravity of the frame.

In a typical unit constructed in accordance with the foregoing, thescreen frame together vs 'th v the gyrating mechanism mounted thereonmay weigh, say, one ton. The masses 29 and 3! may suitably be about 75pounds and 100 pounds, respectively. When these are rotated at a speedof about 1100 R. P. M. an elliptical motion having a major axis slightlyunder half an inch and a minor axis of about of an inch will beproduced. The masses may be rotated in either direction but I have foundthat most efficient screening will take place if the rotation is such asto produce a motion of the screen frame counter to the movement of thematerial along its surface. This means that if the material advancesfrom right to left in Figure 1, the mass 29 should be revolvedcounter-clockwise and the mass 3| clockwise. I have found that the rateof advance of the material along the screen is substantially the same,i. e., about four feet in five seconds, whether the masses are rotatedas specified (Sr in the opposite directions. However, the separation ofthe material is markedly more efficient when the motion of the screen iscounter to the movement of the material than when it is in the directionof this movement.

Referring now to Figures '7 to 15, inclusive,

there is illustrated schematically a number of modified constructionsfor accomplishing substantially the same result, i. e., the productionof a uniform, substantially elliptic motion. In 'each of thesemodifications the arrangement is such as to produce an elliptic motionof the type illustrated in Figure 16, with its major axis inclined at anangle of about 40 to the horizontal in the direction indicated. Theratio of major to minor axis may, however, be .varied in each casetosuit the particular requirements. In Figure 7 there is showna'slightly different arrangement particularly suited for use at pointsat which a smaller amount of head room is available. The screen frame 40in lieu of being supported from below, may be resiliently suspended fromabove by means of a series of soft springs- 4|, one at each corner ofthe frame, having a very low natural period. A pair of shafts 42 and 43,mounted in suitable bearings secured to the under side of the frame, aregeared together by means of gears 44 for rotation in synchronism. Theshafts may be driven ,in any suitable way, as by 'means of a pulleysecured to one of the shafts and a belt connecting it with a source ofpower in the manner shown in Figures 1 and 2. A mass 45 on the shaft 42and a mass 46 on the shaft 43 are revolved in opposite directions tocreate forces of unequal magnitude radially outward from the axes of therespective shafts, these forces being inversely proportional to thedistances of the shaft axes from the center of gravity of the frame. Theother relationships, explained in connection with the forces in FiguresShould it be desired to provide an elliptic motion having a smallerratio between the major and minor axes, the arrangement shown in Figure8 may be adopted. The screen 50 may be resiliently supported orsuspended by soft springs 5|. A pair of shafts 52 and 53, mounted on theframe, are disposed along the line 54 which extends through the centerof gravity of the frame at an angle of 40 to the horizontal or whateverother angle is chosen as the major axis of the elliptic motion. Itisreadily possible with this arrangement to produce an ellipse having afive to one ratio betweenthe major and minor axes without incurring toohigh tooth velocities on gears 55 connecting the shafts. Thus, the axisof shaft 52 may be two units removed from the center of gravity of theframe while the axis of shaft 53 may be three units removed from saidcenter. Masses 56 and 51, secured to the shafts 52 and 53, respectively,will then be in the ratio of three to two and they will be so positionedabove or below the frame or one above and one below, as shown. Theyshould of course. be so disposed that the line bisecting the angleformed between lines connecting the axes of the shafts with the centerof gravity of the frame will be in the direction desired for the majoraxis of the elliptic motion. When the shafts are arranged as shown, theshaft 63 will be disposed along the minor axis of the ellipse. As

in the prior constructions, the centrifugal forces produced by themasses 66 and 61 should be inversely proportional to the distances ofthe axes of the shafts 6| and 62 fromthe center of gravity 68 of theframe. This arrangement might readily be utilized to provide a three toone ellipse by adopting a two to one ratio between the masses.

In Figure 10 there is schematically shown an arrangement in which theunequal masses H and 12 are revolved about the center of gravity of theframe 10. These masses may, if desired,

, both extend longitudinally of their concentric shafts. However, thiswill necessitate the pro-' vision of a large tube 'as the shaft for theouter mass, suflicient to allow the inner mass to rotate within it.Accordingly, I prefer to mount one of the masses, preferably the smallermass 12,

at'each of the ends of a shaft 13 and the other or larger mass Heither'at the ends of or distributed along the hollow shaft 14.surrounding shaft 13. Any suitable gearing maybe employed to connect theshafts I3 and 14 for synchronous v rotation in opposite directions. Forexample, as

best shown in Figure 10a, gears 15 and 16 of the same diameter securedto the ends of the shafts l3 and 14, respectively, may be connected by abevel pinion 11 rotatable in a suitable bracket 18 secured to the side.of the frame 10. Either shaft may be driven through a belt and pulleydrive of the type shown in Figures land 2.

This arrangement allows conveniently for any desired form of ellipticmotion since the' masses may be of any chosen magnitude. In fact, theymay be readily replaceable or interchangeable so thatellipses ofdifferent ratios between major and minor axes may be produced.

A variation of the Figure 10 arrangement is shown in Figure 11. Here,one mass M is mounted upon a shaft 82 carried by the frame 80 atitscenter of gravity. In lieu of a single second mass of differentmagnitude from mass 8|, a pair of equal masses 83 and 84 are provided,these having acombined mass different from, preferably greater than, themass 8|. All three of the masses are rotated at the same speed bygearing 85, the masses 83 and 84 being driven in the same directionandmass BI. in the opposite direction; The axes about which the masses83 and 84 are revolved are at equal distances on opposite sides of thecenter of gravity of the frame; accordingly they provide equalandopposite moments about the center of gravity and there is no tendency torotate the frame.

The masses may be of any chosen magnitude to providean elliptic motionof desired proportions. They maybe disposed either along the shafts orsimply at the ends, depending upon the need for conserving verticalspace. in this type of construction extend along the shafts of amulti-deck screen, it is necessary to increase somewhat the spacingbetween the decks to allow for the free passage of the material alongthe lower deck without interference with the revolving masses.

The foregoing are some of the variations that may be made to provideelliptic motion through the use of counter-rotating forces. It will beapparent that a variety of other modifications may be madeinvolvingdifferent combinations of the various features disclosed and othervariations will suggest themselves to those skilled in the art.

Means not involving counter-rotating forces may also be employed toproduce the desired elliptic motion. In the form schematically shown Iin Figure 12, for example, no rotating mass whatever is employed. Thescreen 90, suspended by means of soft springs 9I at the four corners,hasa rotating shaft 92 extending transversely of the screen through itscenter of gravity. An eccentric 93, secured -to the shaft adjacent itsend, coacts with a strap portion of an arm 94. Adjacent its free endthearm 94 is secured to an inertia mass 95 which extends across the topof the screen and'is suspended from any suit: able support by means ofaspring96. Arm 94 preferably extends through the center of the end of themass and this mass, preferably, has a lift magnitude substantially equalto that 'of the frame 90. A second or auxiliary mass 91 of considerablysmaller magnitude, say about 10% of the mass 95, is slidable along thearm 94 and may be locked in any adjusted position by a set-- a screw orin some other convenient way. It will be understood that the arrangementof eccentric, arm and auxiliary mass is duplicated at the opposite sideof the screen so as to provide balanced forces at the two sides.

Now, as the eccentric 93 is rotated, the screen frame and the inertiamass 95 will be alternately forced apart and drawn together. 91 wereomitted, this'would result in a substantially straight-linereciprocation of the screen frame in the direction of the arm 94.However, the mass 91 induces a considerable deviation from astraight-line motion, the ratio of the longitudinal to the-transversemovement varying with the magnitude and position of'the mass 91. If themass is relatively close to the shaft 92,

When the masses If the massit will be apparent that a considerablerelative movement perpendicular to the arm 94 will take place upon therotation of the eccentric. The portion of this movement that will betaken by the mass itself and the portion that will be taken by thescreen will depend upon the relative weights of the nass and screen. Asthe mass 91 is shifted along the arm 94, further away from the shaft 92,the relative motion between the mass and framein the direction of theminor axis of the ellipse is decreased and hence the part of this motionthat is taken up by the frame is correspondingly smaller. Moreover, theportion of the total, relative -movement in the direction of the minor.axis that .is taken by the frame de-- motion produced may be varied tosuit the particular requirements, either by changing the I magnitude ofthe mass 91 in relation to the mass 95 or by changing the position ofmass 91 in relation to the axis of rotation of the eccentric and thecenter of mass 95. Simply by way of illustration, let, us assume thatthe two masses 91 combined are of half the magnitude of the mass 95 andthe combined weight of all of the masses is equal to that of the frame90. Let us also assume that the masses 91 are arranged substantially at.the eccentric, i. e., atthe center of gravity of the frame. The movementof the frame in a direction along the arm 94 will in that case be equalto the eccentricity of the eccentric since the total, relative movementbe-- tween the frame and masses in this direction will be equallydivided between them. Ina direction at right angles to this, on theother hand, only the masses 91 will oppose the free movement of theeccentric and since these masses are only onethird the weight of theframe, the movement of the frame in this direction will be only abouttransversely through thescreen along its center of gravity and isrotated in any convenient way, as by means of the belt and pulley driveshown in Figures 1 and 2. An eccentric I03 is secured to the shaft I02adjacent each end and cooperates with the strap portion of an arm I04,the upper free end of which is secured to the end of an inertia massI05. 4 The latter is similar to the mass 95 and is suspended from somefixed support by means of a spring I06. A mass I01 is bolted orotherwise secured to the shaft I02, preferably in the manner of themasses 29 and 3I of Figure 1. If desired,- however, a pair ofseparatemasses may be'provided, one at each end of the shaft and secured theretoin any convenient way. In thejoperation of this form of the invention,the eccentric I03 will tend to produce a straight-line movement of thescreen in the direction of the arm I04, the extent of this movementdepending upon therelative weights of the screen and mass I05 and thethrow of the eccentric. If the screen and mass are of equal weight,

the throw of the screen, as a result of the ro-- tation of the eccentricalone, would be, equal to the eccentricity of the'member I03. However,

. the'actual movment of the screen will .be modified by the rotatingmass I01 to an extent de-, pending upon the centrifugal force created bythis mass. Its effect will be added to that of the eccentric in thedirection of the arm I04 so,

that the extent of movement along this-line will be greater than if themass were omitted. At

the same time,however,' the rotating mass will I "impart to the screen amotion transverse to the length of the arm I04.

Accordingly, it will be seen that an elliptical motion will be producedand the ratio of the major to the minor axis of the ellipse will dependupon the magnitude of the centrifugal force created by mass I01 and bythe magnitude of the inertia mass I05. An ellipse of substantially anydesired proportions may be produced in this way. In a typical unit inwhich the frame I weighs a ton, the mass I may be, say, l000pounds andthe mass I01 may be acting against the inertia mass I05, the directionof the major axis of the ellipse will be at right angles to the arm I04rather than along this arm. This condition is illustratedin Figure 14,

in which the mass 17a is indicated as of considerable magnitude. In thisconstruction the mass 905 and the eccentric tend to restrict themovement of the screen in the direction along the armto an amount lessthan the movement which the rotating mass would of itself tend to impartto the screen. For this purpose the typical. unit specified above forFigure 13 might be modified to provide a somewhat smaller inertia massM511 and to employ a rotating mass of, say, 200 pounds.

A still further modification is illustrated in Figure 15. Here thedesired motion of the screen is derived from the use of a singlerotating mass and one or more inertia masses having pivotal connectionwith the live frame. The screen or other body 0, as before, is supportedor suspended by means of soft springs III, one arranged at each of thefour corners of the frame.

A shaft IIZ extending transversely of the screen passes through thecenter of gravity. A mass H3 is secured to this shaft and develops asuitable centrifugal force for gyrating the screen upon revolution ofthe shaft at an appropriate speed. At each side of thescreen there isprovided a pair of arms H4 connected pivotally with the screen at pointsH5, arranged in the same plane as the center of gravity of the screenand spaced equal distances from the center of gravity. At-their upperends the arms II4 are secured to inertia masses H6 suspended from anysuitable support by means of springs I". It

will be apparent that as the mass I I3 rotates,-

it will impart substantially its full effect to the screen alongthe'line H8 whereas in a direction transverse to this, i. e., parallelwith the arms N4, the centrifugal force of mass H3 will be opposed bythe inertia of the masses 6. N0 turning moments will be applied to thescreen due to the fact that the mass 3 acts upon the screen directly atits center of gravity while the inertia masses impart their retardingeffects along parallel lines. and in the same direction at ints equallyspaced from the center of grav-v rty and on opposite sides thereof. Itis assumed, of course, that the inertia masses H6 will be of equalmagnitude so that the retarding forces will be equal.

It will be clear from the foregoing that the path of movement of thescreen II 0 will be elliptical and the ratio-of the major to the minoraxis of the ellipse. will depend upon the relation between the Weight ofthe live frame and the sum of the Weights II6.' The larger the masses H6in proportion to the weight of the frame, the greater will be the ratiobetween the major and minor axes of the ellipse. In lieu ofproviddepends, of course, upon the magnitude of the inertia forceproduced by the mass H3.

The term primary force as used herein and in the appended claims isdefined as a force applied through, or in conjunction with, an externalsource of power as distinguished from mere reactive forces. For example,the rotating masses and the inertia masses in conjunction withpositively driven eccentrics apply primary forces to the suspended body.The suspending means apply merely reactive forces.

In connection with all of the forms of the in-' vention which have beenmerely schematically illustrated, it will be understood that the variousdevices shown will be duplicated at the two sides of the screen framewherever required or desirable to provide a well balanced structure.

tating masses provided adjacent the ends of a shaft, eccentrics, and thevarious arms-connecting the inertia masses with the screen frames.

While a variety of diiferentconstructions, ca-

screen -or similar body along an elliptical path, have been described inconsiderable detail, it will be understood that numerous othermodifications than those specifically suggested may be made withoutdeparting from the general principles and scope of the invention. Theterms and expressions employed herein have been used stantiallyelliptical motion to all portions of said body, said means'comprisingeccentrically mountnitude mounted onsaid body.

3." In apparatus of the class described a main ed oppositely rotatingmasses of unequal magframe, a body supported by said frame, and meansfor imparting a uniform substantially This applies, for example, to thesupporting springs,

the gearing between counter-rotating shafts, ro-

.pable of imparting a gyratory movement to a elliptical motion to allportions of said body,

said means comprising eccentrically mounted,

oppositely rotating masses of unequal magnitude carriedby said body, theaxis of rotation of said masses being substantiallyat the center ofgravity of said body.

4. In apparatus of the class described a main frame, a body, resilientmeans for supporting said body from said frame, and means for impartinga uniform substantially elliptical mo tion to all portions of said body,said means comprising a plurality of masses mounted on said body torevolve in opposite directions, said masses being of different magnitudeand revolving about difierent axes eccentric to the centers of gravityof the masses.

5. In apparatus of the class described a main.

frame, a body, resilient means for supporting said body from said frame,and means for imparting a uniform substantially elliptical motion to allportions of said body, said means comprising a plurality of massesmounted on said body to revolve in opposite, directions, said massesbeing of different magnitude and revolving about different axeseccentric to the centers of gravity of the masses and to the center ofgravity of said body.

6. In apparatus of the class described a main frame, a body, resilientmeans for supporting said body from said frame, and means for impartinga uniform substantially elliptical motion to all portions of saidbody,said means compris-' ing a plurality of masses revolving in oppositedirections, said masses being of diiferent magnitude and revolving aboutdifferent axes eccentrio to the centers of gravity of the masses and tothe center of gravity of said body the mag nitude of said masses beinginversely proportional'to the distances between their axes of rotationand the center of gravity of the body.

'7. In apparatus of the .class described a main frame, a body, resilientmeans for supporting said body from said frame, and means for im-'parting a uniform substantially elliptical motion to all portions ofsaid body, said means comprising 'a plurality of masses revolving inopposite directions, said masses being of different magnitude andrevolving about different axes eccentric to the centers of gravity ofthe masses and to the center'of gravity of said body, the magnitude ofsaid masses being inversely proportional to the distances between theiraxes of rotation and the center of gravity of the body,

said masses being rotated at the same speeds and each having its axis-ofrotation at the same distance from its center of gravity asthe other. 8.In apparatus of the class described a main frame, a body, resilientmeans for supporting said body from said frame, and means for impartingauniform substantially elliptical motion to all portions of saidbody,said means comprising a plurality of masses revolving in oppositedirections, said masses being of different magnitude and revolving aboutdifferent'axes eccentric to the centers of gravity of the masses and tothe center of gravity of said body, the magnitude of said masses beinginversely proportional to the distances between their axes of rotationand the center of gravity of the body, said masses being rotated at thesame speedsand each having its axis of rotation at the same distancefrom its center of gravity as the other, the arrangement of said massesbeing such that when a straight line passing through the axis ofrotation and the center of gravity of one mass tive to apply resultantforces at the center of gravity of said body such as to produce auniform, substantially elliptical motion at all points of said body.

10. In apparatus of the class described a gymtory body, means forresiliently supporting said body, means'for imparting a constantrotatingforce to said body about a substantially horizontal axis, and means forimparting a second force to said body to modify the effect of said firstmentioned force, said two force imparting means. being constructed andarranged to apply a resultant force to said body of constantly changingdirection and magnitude.

11. In apparatus of the class described a gymtory body, means forresiliently supporting said body, and a plurality of means for impartingI constantrotating forces of different magnitude to said body atdifferent points, the forces rotating about substantiallyhorizontalaxes, said force imparting means being constructed and arranged to applya resultant force to said body of constantly changing direction-andmagnitude.

12. In apparatus of the class described a gymtory body, means forresiliently supporting said body, and means for imparting a plurality offorces to said body substantially at the center of gravity thereof, theforces rotating about substantially horizontal axes, the resultant ofsaid forces being of constantly changing magnitude and direction; 13. Inapparatus of the class described a gymtory body, means for resilientlysupporting said body, rotating means for imparting a force to said body,and'inertia means connected with said body, said rotating means and saidinertia means being so constructed and arranged as to impart to saidbody the effect of aforce constantly changing in direction and magnitudeapplied at the center of gravity of the body. V

14. In apparatus of the class described a gymtory body, meansfor=supporting said body for gyratory movement, and means for impartingto said body at a pair of points spaced different distances fromthecenter of gravity thereof rotating forces of constant magnitude, saidforces being of unequal magnitude and inversely proportional to thedistances of the points of application from the center of gravity ofsaid body.

15. In apparatus of the class described a 'gyra-' 'torybody, .means forsupporting said body for gyratory movement, and means for imparting tosaid body at a pair of points spaced different distances from the centerof gravity thereof rotating forces of'constant magnitude said forcesbeing of unequalmagnitude and inversely proportional to the distances ofthe points of application from the center of gravity of said body, andsaid forces being rotated in synchronism in opposite directions andbeing alined with said said body at a pair of points spaced differentdistances from the center of gravity thereof rotating forces of constantmagnitude, said forces being of. unequal magnitude and inverselyproportional to the distances of the points of application from thecenter of gravity of said body, and said forces being rotated insynchronism in opposite directions and, being alined with said center ofgravity at the same' instant, a line bisecting the angle between saidforces when alined with the centerof gravity of said "body beingdisposed at an angle of about 40 to the horizontal.

17. In apparatus of the class described a gyratory body, means forsupporting said body for gyratory movement, means for imparting to saidbody at substantially the center of gravity thereof a force of constantmagnitude but continually changing in direction through a,predeterminedcycle, and means for imposing a greater inertia force in opposition tosaid force in certain directions than in others.

18. In apparatus of the class described a gyra-.

tory body,- means for supporting said body for gyratory movement, meansfor imparting to said body at substantially the center of gravitythereof a force of constant magnitude but continually plurality ofpoints for a free gyratory motion,

means for imparting a constantly rotating force of invariable magnitudeto said body, and means for imparting a modifying force to said body ata point removed from said plurality of points to produce a uniform,substantially elliptical motion at all points of said body.

20. In apparatus of the class described a gymtory body, means forsupporting said body for gyratory movement, a shaft extending throughsaid body at its center of gravity, an eccentric mounted on said shaft,an inertia mass freely suspended adjacent saidbody, an arm connectedwith said mass and having a strap surrounding said eccentric, meansforrotating said shaft and eccentric to produce relative movement betweensaid body and massin the direction of said arm, and means for inducingmovement ofsaid body in a direction transverse to said arm.

21. In apparatus of the class described a gyratory body, means forsupporting said body for gyratory movement, a shaft extending throughsaid body at its center of gravity, an. eccentric mounted on said shaft,an inertia mass freely suspended adjacent said body, an arm connectedwith saidmass and having a strap surrounding said eccentric, means forrotating saidsh'aft and eccentric to produce relative movement betweensaid body and mass in the direction of said arm,

and an auxiliary mass adjustably mountedon said arm.

22. In apparatus of the class described a gyratory body, means forsupporting said body for gyratory movement, a shaft extending throughsaid body at its center of gravity, an eccentric mounted on said shaft,an inertia mass freely suspended ,adjacent said body, an arm connectedwith said mass and having a strap surrounding said eccentric, means forrotating said shaft and eccentric to produce. relative movement betweenbody throughout.

' gyratory movement, a shaft extending through said body at its centerof gravity, a mass secured to said shaft for rotation therewith, inertiamass means suspended for free movement adjacent said body, and meansconnecting said body with said inertia mass means.

24. In apparatus of the class described a gyratory body, means forsupporting said body for gyratory movement, a shaft extending throughsaid body at its center of gravity, a pair of shafts parallel with saidfirst mentioned shaft extending through said body on opposite sides ofsaid first mentioned shaft and spaced equally therefrom, means forrotating said shafts at the same speed, the shafts of said pair rotatingin the same direction and opposite to the rotation of said firstmentioned shaft, and a mass secured to each of said shafts for rotationtherewith, the masses secured to the shafts of said pair being of equalmagnitude.

25. In apparatus of the class described a gyratory body, means forsupporting said body for gyratory movement, and means for imparting auniform, substantially elliptical movement to all portions of said body,said last mentioned means comprising a plurality 'of parallel shaftsmounted on said body in a plane passing through-the centerv of gravitythereof, means for rotating said shafts, and a mass secured to each ofsaid shafts for rotation therewith.

26. In apparatus of the class described a gyratory body, means forsupportingsaid body for gyratory movement, and means for imparting auniform, substantially elliptical movement to all portions of said body,said last mentioned means comprising a plurality of parallel shaftsmounted onsaid body in a plane passing through the center of gravitythereof, means for rotating said.

shafts, and a mass secured to each of said shafts for rotationtherewith, said shafts being rotated in opposite directions and saidmasses being of unequal magnitude.

27. In apparatus of the class described, a gym tory body, softlyresilient means for supporting said body for free gyratory motion, andmeans separate from saidsupportingmeans comprising moving massesconnected to said body whose dynamic effect imparts resultant force tosaid body in such changing direction and magnitude as to produce asubstantially uniform and substantially elliptical motion of the bodythroughout.

8. In apparatus of the class described a gyratory body,instrumentalities for supporting said' body for gyratory motion, andmechanism separate from said instrumentalities connected with said bodyfor producing a substantially uniform and substantially ellipticalmotion of the body throughout.

29. In apparatus of the class described a gymtory body,instrumentalities for supporting said body for gyratory motion, andmechanism separate from said instrumentalities including a rotatingmember and a moving mass and connected with said body for producing asubstantially uni- I form and substantially elliptical motion of theSAMUEL D. ROBINS.,

